public class HashBuck2 <K,V>{
    static class Node<K, V> {
        public K key;
        public V val;
        public Node<K, V> next;

        public Node(K key, V val) {
            this.key = key;
            this.val = val;
        }
    }

    public Node<K,V> array[];
    public int usedSize;
    public static final float DEFAULT_LOAD_FACTOR = 0.75f;

    public HashBuck2() {
        array = (Node<K, V>[])new Node[10];
    }

    public void put(K key, V val) {
        int hash = key.hashCode();
        int index = hash % array.length;
        Node<K,V> cur = array[index];
        while (cur != null) {
            if(cur.key == key) {
                //更新 val
                cur.val = val;
                return;
            }
            cur = cur.next;
        }

        Node<K,V> node = new Node<>(key,val);
        node.next = array[index];
        array[index] = node;
        usedSize++;

        if(doLoadFactor() > DEFAULT_LOAD_FACTOR) {
            //扩容
            resize();
        }
    }

    private void resize() {
        Node<K,V> [] newArray = new Node[array.length*2];

        //遍历原来数组
        for(int i = 0; i<array.length; i++) {
            Node<K,V> cur = array[i];
            //遍历每个数组元素(链表)
            while (cur != null) {
                Node<K,V> tmp = cur.next;
                int hash = cur.key.hashCode();
                int newIndex = hash%newArray.length;
                //采用头插法 插入到新数组的newIndex下标
                cur.next = newArray[newIndex];
                newArray[newIndex] = cur;
                cur = tmp;
            }
        }

        array = newArray;
    }

    private float doLoadFactor() {
        return usedSize * 1.0f / array.length;
    }


    public V get(K key) {
        int hash = key.hashCode();
        int index = hash % array.length;
        Node<K,V> cur = array[index];
        while (cur != null) {
            if(cur.key.equals(key)) {
                return cur.val;
            }
            cur = cur.next;
        }
        return null;
    }
}
